fix(stdlib): io test

[notJoon]

Description

Fixed a failing test in the io package. Additionally, I activated some previously commented-out tests by bypassing the need for os.CreateTemp using bytes.Buffer.

Contributors' checklist...

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests
• Added new benchmarks to generated graphs, if any. More info here.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.57%. Comparing base (5e71837) to head (bcd6b19).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2898      +/-   ##
==========================================
+ Coverage   63.39%   63.57%   +0.18%     
==========================================
  Files         565      565              
  Lines       79390    79471      +81     
==========================================
+ Hits        50329    50524     +195     
+ Misses      25673    25564     -109     
+ Partials     3388     3383       -5     

Flag	Coverage Δ
contribs/gnodev	60.57% <ø> (ø)
contribs/gnofaucet	14.82% <ø> (ø)
gno.land	67.37% <ø> (ø)
gnovm	67.86% <ø> (ø)
misc/genstd	79.72% <ø> (ø)
tm2	62.47% <ø> (+0.03%)	⬆️

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[thehowl]

Instead of exporting the errors, I'd rather we kept them unexported and put the test in package io (instead of io_test).

[notJoon]

Instead of exporting the errors, I'd rather we kept them unexported and put the test in package io (instead of io_test).

Changed the error types to private and modified the test package declaration from io_test to io.

The ErrShortWrite, EOF, ErrUnexpectedEOF, and ErrNoProgress errors remain public, as they are also used in the bufio package.

a63bb39